A model of normal fault interaction based on observations and theory

Recent earthquakes have shown that fault interaction can affect rupture sequences. However, few criteria are currently available to determine which fault segments are strongly interacting. Here we develop a simple, elastic-plastic model of fault interaction that can assess degrees of interaction within a population of faults using only map traces or displacement profiles. In this model, faults interact through their stress fields. Examination of map traces and displacement profiles from 65 pairs of small (L < 1 m) interacting faults shows that faults respond to reductions in shear stress around other nearby faults by accumulating anomalous displacement. There is a positive linear relationship between the amount of stress reduction felt at a tip and anomalous displacement accumulation near this tip. In addition, there is a stress reduction region around faults into which other faults do not propagate and nucleate. The linear relationship and limit to propagation may be used to estimate degrees of interaction within a population of faults. We check for model consistency with observations of separation and overlap, displacement–length ratios, and rift-basin scale fault growth.